Several diseases are associated with autoimmune Addison's disease and may thus suggest the diagnosis. These are now classified as autoimmune polyglandular deficiency type I and type II (see Fig. 9.1). The human leucocyte antigens (HLA) DR3 and DR4 are strongly associated with autoimmune Addison's disease. The relative risks are 6 for DR3, 4.6 for DR4, and 26.5 for DR3/DR4 heterozygotes. These risks are similar to those of the HLA associations of type I diabetes mellitus. Interestingly, the HLA associations of patients with autoimmune polyglandular deficiency type I are not different to controls, thus suggesting that this condition has a different aetiology.
